Weight loss abstract
Freshly picked washed mushrooms are subject to a modified atmosphere
and infused with a suspension containing a particulate microscopic
heat stable material. Upon blanching in boiling water the weight
loss experienced is reduced from a normal 24% to 33% loss to between
a 2% loss and a 5% or more weight gain.
Weight loss claims
What we claim is:
1. A method for processing mushrooms for reducing shrinkage during
subsequent cooking comprising the steps of:
introducing the mushrooms into a sealable container whose contents
include a water suspension of an effective amount of an edible microscopic
sized heat stable non water soluble solid particulate hydrophilic
material, with an average particle size of less than 2 microns
subjecting the contents of the container to at least one application
of a pressure whose value is sufficiently above atmospheric pressure
to cause compression of the air entrained between the mycellular
strands of the mushrooms tissue
wherein, the pressure is at least 10 psi above atmospheric pressure,
and the microscopic particulate material is at least 0.5% by weight
of the suspension
submerging the mushrooms in said water suspension while rapidly
restoring the pressure in the container to atmospheric pressure,
at a rate rapid enough to cause a portion of the compressed air
entrained between the mycellular strands to be expelled from the
said expelled air being replaced within the mushrooms by a quantity
of the water suspension, and
removing the mushrooms from the container.
2. A method as in claim 1 further comprising the steps of:
subjecting the contents of the container to an additional application
of pressure, at least 10 psi above atmospheric pressure, and again
rapidly restoring the pressure in the container to atmospheric pressure,
causing additional air between the mycellular strands to be expelled
and replaced by an additional portion of the suspension, prior to
the removal of the mushrooms from the container.
3. A method for processing mushrooms as in claim 2; wherein,
the concentration of the microscopic particulate hydrophilic material
in the suspension is less than 10% by weight.
4. A method for processing mushrooms as in claim 3, wherein,
the microscopic sized particulate hydrophilic material is microcrystalline
5. A method for processing mushrooms as in claim 1; wherein,
the rapid restoration of pressure is at a rate of at least 3 psi
6. A method as in claim 1 wherein,
the water suspension additionally includes a protective hydrocolloid
to aid in suspension of the said particulate material.
7. A method as in claim 4 wherein,
the water suspension additionally includes a protective hydrocolloid
to aid in the dispersion of the microcrystalline cellulose.
8. A method for processing mushrooms with reduced shrinkage during
subsequent cooking comprising the steps of:
introducing the mushrooms into a sealable container whose contents
include a water suspension of at least 0.5% by weight of an edible
microscopic sized, heat stable, non water soluble, solid, particulate,
hydrophilic material, with an average particle size of less than
subjecting the contents of the container to a vacuum of at least
20 inches of mercury, to remove a portion of the air entrained in
the intermycellular spaces of the mushrooms
submerging the mushrooms in the water suspension while restoring
the pressure in the container to atmospheric pressure causing a
portion of the water suspension to replace the air removed from
the intermycellular spaces, and
removing the mushrooms from the container.
9. A method for processing mushrooms as in claim 8, further comprising
the steps of:
subjecting the contents of the container to an additional application
of vacuum of at least 20 inches of mercury and again restoring the
pressure to atmospheric pressure while submerging the mushrooms
in the suspension, prior to removal of the mushrooms from the container.
10. A method for processing mushrooms as in claim 8, wherein,
the concentration of the said particulate hydrophilic material
in the water suspension is less than 10% by weight.
11. A method for processing mushrooms as in claim 8, wherein
the vacuum applied is at least 28 inches of mercury.
12. A method as in claim 8 wherein,
the said particulate is selected from the group comprising microcrystalline
cellulose, microcrystalline chiten, silica dioxide, dry corn, dry
rice, oriental rice paper and dry spaghetti.
13. A method as in claim 12 wherein,
the aqueous suspension additionally contains a protective hydrocolloid
to aid in dispersion of the said particulates.
14. The mushroom product produced by the process of claim 1.
Weight loss description
BACKGROUND OF THE INVENTION
This invention is a continuation-in-part-application of U.S. patent
application Ser. No. 46,078, filed June 6, 1979, now abandoned and
copending U.S. patent application Ser. No. 266,222, filed May 11,
1981 now abandoned.
Mushrooms commonly lose approximately 25% to 30% or more of their
fresh weight when subject to the blanching process prior to canning.
The blanching process is designed to inactivate certain enzymes
and partially sterilize the mushrooms and involves either steam
or boiling water cooking for approximately five (5) minutes to bring
the internal temperature to 180.degree. F. or above.
Sterilization after canning normally results in an additional 10%
to 15% weight loss. Sterilization is normally accomplished in a
pressure vessel and involves bringing the temperature at the middle
of the sealed can to 250.degree. F. and holding this temperature
a sufficient time to destroy thermophylic organisms which may be
present and complete the sterilization.
The combination of these two processes result in an expected weight
loss during canning of mushrooms of 35% to over 40%.
The extreme weight loss sets mushrooms apart from other vegetables
as does the fact that they are a macro fungi rather than a chlorophyl
The weight loss that is experienced in the canning process makes
the canned product more expensive than fresh mushrooms. The canned
mushroom, upon further cooking such as sauteing, still experiences
a further weight loss.
Several processes have been proposed for reducing the weight loss
experienced during canning mushrooms. U.S. Pat. No. 3,843,810, to
Fehmerling proposes applying a vacuum down to lower than 13 mm of
mercury in a slow, controlled descent followed by at least one hour
at the minimum pressure then a slow increase in pressure to ambient,
while soaking the mushrooms in a water solution. The process takes
a minimum of two hours in the vacuum and preferably three hours.
The average yield after blanching given by Fehmerling with a three
hour process is given as 84%. Additionally, Fehmerling shows a series
of comparisons between his process and other vacuum processes.
The best previous process known to the present inventors is shown
in U.S. Pat. No. 4,143,167, to Blanchaud, et al. This process also
uses a vacuum down to approximately 50 mm to 60 mm of mercury in
a solution wherein is disolved 1% to 6% dried egg albumin or equivelent.
The albumin is then coagulated during the blanching process. This
treatment does succeed in reducing the weight loss somewhat, however,
the resulting product has objectionable coagulated albumin hanging
from it and the texture is noticably tough and rubbery.
Mushrooms, after harvest, are normally commercially stored at approximately
32.degree. F. to retard further respiration which would result in
opening of the veil which makes them less desirable and to reduce
the weight loss during storage since mushrooms continue to respire
It is known to commercial canners and shown in the experiments
of McArdle, et al., in 1962, that there is a relationship between
the length of post harvest storage and the amount of weight loss
experienced during canning. The small reduction of the weight loss
is partially offset by the weight loss in storage due to respiration
of the mushroom along with deterioration of color and blemishing
and the increased number of "opens" or lower grade mushrooms
from extended storage. Even this slight reduction in weight loss
prompts most mushrooms canneries to store fresh mushrooms at about
32+ for two to three days prior to canning.
SUMMARY OF THE INVENTION
The present invention provides a rapid, economical procedure for
substantially reducing the weight loss presently experienced in
canning or cooking mushrooms. This is brought about by use of a
rapid vacuum and/or pressure assisted impregnation into the mushroom
of a microscopic sized particulate hydrophillic material in suspension
in a water based vehicle. This rapid infusion raises the weight
of the mushroom by up to 50% or more of their fresh weight as in
other known vacuum hydrating processes. However, subsequent blanching
of the mushrooms after treatment results in a loss back to close
to their fresh weight rather than a loss close to that of untreated
mushrooms as in the previous process. Canning and retorting of these
treated, blanched mushrooms cause an additional weight loss but
the total weight loss in canning is reduced to approximately 10%
to 15% of the original fresh weight as opposed to 33% to 40% weight
loss which is experienced by conventional processing methods.
The resulting mushrooms, in addition to the reduction in weight
loss, have a texture both before and after subsequent cooking which
is markedly superior to presently available canned mushrooms and
is often judged better than fresh mushrooms that have been similarly
cooked by common methods such as sauteing or in a tomato sauce.
The method and materials are fully explained in the following description
of the preferred embodiments and drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 thru 3, illustrate the effects of variations in methods
and material concentrations on a preferred embodiment of the process.
FIG. 4 illustrates the effect of extended cold storage of mushrooms
on the process results.
FIGS. 5 and 6 illustrate the effects of particle size on the process
using a variety of materials having other physical properties in
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The improved processing method comprises a vacuum or pressure assisted
infusion of a microscopic particulate hydrophilic material into
the mushroom. A variety of materials are suitable for this process
and a number of them are discussed in the balance of the disclosure.
A particular material that combines all of the properties required
is microcrystalline cellulose as described in U.S. Pat. No. 3,023,104.
The particular type of microcrystalline cellulose that has been
found to be most readily usable for the process is marketed by FMC
Corporation under the trade name of AVICEL type CL-611, which combines
microcrystalline cellulose in an average particule size of about
0.2 microns with sodium carboxymethyl cellulose gum to aid in ready
dispersion in liquid. The manufacturer's tests indicate that approximately
60% to 70% of the CL-611 material is 0.2 microns in size with the
balance being of larger sizes ranging up to approximately 20 microns.
Microcrystalline cellulose is a minute particulate aggregate widely
used in the food industry as a bulking agent, in dietary foods and
as a thickening and stabilizing agent in sauces, etc. This material
is used in the majority of the tests which illustrate the parameters
of the invention and a number of other materials are included in
tests illustrating the importance of the particular combination
of physical properties in any material in order to be successfully
applied to the process.
The following examples are presented to illustrate the particulars
of the present invention and alternative methods for the accomplishment
of the desired ends.
During the course of the tests, mushrooms from various growers
were randomly selected. The mushrooms used for the tests were less
than 24 hours post harvest, unless otherwise noted, and had been
stored in commercial facilities at a temperature of approximately
32.degree. F. and high relative humidity. Weight changes during
the tests are expressed as percentage of the beginning weights of
the samples to provide ready comparison. The percentages in all
cases are averages obtained from multiple repetitions of the tests.
All tests were performed in the following manner unless otherwise
Samples were drawn from standard 10 pound boxes as delivered to
the processor by the grower. Weights were recorded using a laboratory
scale. Samples were all washed by tumbling in fresh water for three
minutes, closely approximating the initial processing in commercial
Samples were then drained for three minutes on a slanted screen
and weighted again.
The selected treatment method was performed and the sample was
again drained and weighed.
The samples were plunged into boiling water for five minutes then
cooled in water for three minutes to approximately 80.degree. F.
internal temperature. The sample was again drained and weighed.
Sample No. 1, is a control and no processing was used other than
washing and blanching.
Sample No. 2, was submerged in water and subjected to a vacuum
of approximately 29.5 inches of mercury for five minutes. The vacuum
was released for one minute, reapplied for five minutes, and released
Sample No. 3, was treated the same as No. 2, except a 2% by weight
solution of Carrageenan (an algin derivative non heat stable gel)
in water was used.
Sample No. 4, was submerged in a 4% by weight suspension of AVICEL
type CL-611 and subjected to an overpressure of 10 psi for 30 seconds.
The pressure was rapidly released at a rate of greater than 3 psi
per second, left off for 10 seconds and applied a second time for
30 seconds, rapidly released, left off for 10 seconds, reapplied
for 30 seconds and again released.
Sample No. 5, was treated the same as No. 4, except a pressure
of 15 psi was used.
Sample No. 6, was treated the same as No. 4, except a pressure
of 20 psi was used.
Sample No. 7, was treated the same as No. 4, except a pressure
of 25 psi was used.
Sample No. 8, was treated the same as No. 4, except a pressure
of 30 psi was used.
Sample No. 9, was treated the same as No. 4, except a pressure
of 80 psi was used.
Sample No. 10, was submerged in a 4% by weight suspension of AVICEL
type CL-611 in water, subjected to a vacuum of approximately 29.5
inches of mercury for five minutes. The vacuum was released and
the mushrooms were allowed to stand in the suspension for one minute.
Sample No. 11, was submerged in a 4% by weight suspension of AVICEL
type CL-611 in water and subjected to a vacuum of approximately
29.5 inches of mercury for five minutes. The vacuum was released
for one minute and reapplied for five minutes. The vacuum was again
released and the mushrooms allowed to stand in the suspension for
The results of the various comparative tests are summarized in
TABLE 1* __________________________________________________________________________
AFTER AFTER AFTER SAMPLE START WASH TREATMENT BLANCH & COOL
1 100 113 -- 74 Control 2 100 112 155 75 Water & Vacuum 3 100
112 156 77 Carrageman & Vacuum 4 100 112 145 86 3 .times. 10
psi 5 100 113 148 90 3 .times. 15 psi 6 100 112 147 91 3 .times.
20 psi 7 100 113 148 90 3 .times. 25 psi 8 100 112 146 88 3 .times.
30 psi 9 100 111 145 89 3 .times. 80 psi 10 100 112 152 100 Vacuum
1 times 11 100 113 160 105 Vacuum 2 times __________________________________________________________________________
*(weights expressed as percentage of fresh weight).
A vacuum of approximately 29.5 inches of mercury was chosen since
it is fairly easily obtainable with laboratory equipment. The use
of two 5 minute time periods in the vacuum was chosen since it can
reasonably be assured that complete evacuation to the selected level
will have been reliably repeated by this procedure. As illustrated
in further testing, these levels and durations of vacuum are widely
variable while still obtaining the desired results.
It is evident from the tests performed that infusing a particulate
heat stable material in a suspension such as microcrystalline cellulose
codried with a protective hydrocolloid as found in AVICEL type CL-611
produced a remarkable reduction in the weight loss experienced.
The infusion of water or a non heat stable gel such as carregeenan
has little effect on the shrinkage experienced when using a similar
It is seen that producing the infusion by means of drawing and
releasing a vacuum is a superior method to utilizing pressure to
produce the infusion. It is particularly interesting to note, however,
that a moderate pressure of from 15 psi to 30 psi over the ambient
followed by rapid release of the pressure and preferably repeating
the pressure and release two or three times does produce an infusion
into the mushroom to a degree sufficient to sizeably reduce the
shrinkage during blanching. The use of pressure to produce an infusion
in mushrooms is a completely new approach in mushroom processing.
Mushrooms are a porous, resilient plant product that are considered
to be very delicate and are particularly susceptible to bruising.
For this reason, transport of mushrooms during processing is generally
done by water flume rather than by conveyors or other means to reduce
bruising and the resulting lowering of the quality of the product.
The use of overpressure and rapid release to produce the infusion
in the mushrooms resulted in no detectable bruising or damage to
the mushrooms whatsoever as could be determined from careful examination.
The rapid accomplishment of an infusion by means of pressure rather
than vacuum is an unexpected and valuable discovery.
In many cases a moderate overpressure of between 15 psi and 30
psi is much easier to accomplish than drawing a considerable vacuum
in commercial size applications. It has also been discovered that
overpressure above approximately 30 psi to 35 psi has little or
no added benefit as illustrated by sample No. 9, wherein 80 psi
overpressure was used with no significant difference in the weight
of the mushrooms after treatment or after blanch when compared to
the results obtained with pressures of 10 psi to 30 psi.
Using a single pressure application and rapid release the shrink
reduction after blanch was approximately 80% of the reduction experienced
after three pressure and release cycles. Two pressure and rapid
release cycles accomplished over 90% of the results using three
cycles. More than three pressure and rapid release cycles resulted
in no significant repeatable improvement over that obtained in three
After the first pressure application and rapid release profuse
bubbling could be observed from air expelled from the mushrooms.
After the second pressure and release cycle moderate bubbling was
observed and after the third pressure and release cycle sparse bubbling
was seen. Only a minute amount of bubbling was observed after additional
pressure and release cycles.
The rapid release of the applied pressure apparently causes the
mushroom and the air compressed within it to rebound in an elastic
manner resulting in a portion of the air being expelled and replaced
by the liquid suspension. After three of these pulse-like cycles,
virtually all of the air that can be expelled by this method has
apparently escaped and been replaced by the surrounding suspension.
It has been observed during these tests that after a single vacuum
application and release approximately 20% of the mushrooms remain
floating. After drawing and releasing the vacuum the second time
virtually 100% of the mushrooms sank to the bottom of the liquid
indicating virtually complete saturation.
Due to the fact that mushrooms commonly float in water by reason
of large amounts of air incorporated into the intermycellular spaces
it is probable that these mushrooms still floating after the first
vacuum application were slightly above the level of the liquid when
the vacuum was broken and drew some air back into the spaces rather
than the liquid. The use of a second vacuum application eleminated
this potential source of variations in the results of the tests.
Tests were also made combining the use of single and multiple low
overpressure applications either before or after a single vacuum
application. The results of these tests were similar to those given
for samples 5 thru 10 with the majority giving results close to
those of sample 10.
Mushrooms treated by the process of example No. 11, were further
processed by actual canning and sterilization in commercial equipment
along with control samples from the same lot of mushrooms which
were conventionally processed. Beginning weights, weights after
blanching, and weights of blanched mushrooms placed in each can
prior to sterilization were recorded. After the cans were sealed,
commerical process sterilization equipment was used to bring the
temperature at the center of the cans to 250.degree. F. and hold
this temperature a sufficient time to fully sterilize the contents.
Sample cans of the treated and control mushrooms were opened, drained
and weighed after one day storage and one week storage. The conventionally
processed mushrooms experienced a total shrinkage of between 32%
and 37% of their fresh weight. The mushrooms processed according
to the procedure in example No. 11, experienced a total shrinkage
of between 11% and 14% of their fresh weight.
Blind taste and appearance comparative tests were conducted using
subjects involved in the mushroom industry, either as growers, or
in processing, or marketing. Samples of canned mushrooms processed
conventionally and by the process of example No. 11, were served
as they came from the can, cooked by sauteing, and cooked in a commercially
available tomato sauce for spaghetti.
The mushrooms prepared by the process of example No. 11, were chosen
unanimously for better color and appearance. There was no discernible
difference expressed as regards taste. Surprisingly, the mushrooms
prepared by the process of example No. 11, were unanimously remarked
upon as being superior in texture, retaining a fresh uniform tender
texture throughout while the conventionally processed mushrooms
had a characteristic toughness of skin after being sauted and especially
after cooking in the tomato sauce.
Additional tests were conducted with mushrooms processed according
to the procedures of example No. 11, and frozen.
Frozen mushrooms are used commercially by restaurants, and in ready
to cook frozen foods such as pizzas.
Fresh frozen mushrooms, when cooked, lose a considerable amount
of water weight. This is particularly objectional in items such
as frozen pizzas wherein the mushrooms often form a puddle of almost
boiling water with noticeable shrinking. Weight loss from cooking
fresh frozen mushrooms average from 40% to 50% of the fresh weight.
Weight loss from cooking mushrooms treated and blanched according
to the process of example No. 11, and then frozen average between
14% and 22% of their beginning fresh weight. This remarkable reduction
in weight loss was accompanied by an equal reduction in the puddling
and visably noticeable shrinkage experienced. Additionally, the
texture of the frozen mushrooms processed according to the present
invention was tender and succulent as opposed to the noticeable
toughening of the conventionally frozen mushrooms.
Mushrooms prepared according to the process of example No. 11,
but not blanched were frozen. Upon subsequent cooking the percentage
of weight loss from the infused weight was between 40% and 50% or
generally comparable to the shrinkage of fresh frozen mushrooms.
However, the yield from one pound of fresh mushrooms is considerably
greater when treated according to the present invention and then
frozen, than if just fresh frozen as is illustrated in Table 2.
TABLE 2** ______________________________________ AFTER PRO- CES-
FROZEN COOKED START SING WEIGHT WEIGHT ______________________________________
PROCESSED 100 150 150 75 to 90 BY EXAMPLE #11 NORMAL 100 110 110
50 to 60 COMMERCIAL PROCESSING ______________________________________
**(weights expressed as percentage of fresh weight)
As can be seen in Table 2, equal batches of mushrooms were conventionally
fresh frozen, and processed the same as sample No. 11, and frozen
without being blanched. When later cooked, the fresh frozen mushrooms
yielded a cooked weight of 50% to 60% of their fresh weight. The
sample that was infused as in sample No. 11, and frozen without
blanching yielded a cooked weight of 75% to 90% of their fresh weight.
Additional testing was performed to determine the effect of variations
in the process in terms of particular concentrations, vacuum depth
and duration under vacuum. These tests are summarized in graphic
form in FIGS. 1, 2 and 3. In these tests the mushrooms were physically
held below the liquid level during vacuum release to avoid possible
variations due to re-entrainment of air.
In FIG. 1, the concentration of microcrystalline cellulose as AVICEL
CL-611, was varied from 0.5% to 5% weight of the water vehicle used.
A vacuum application of approximately 29.5 inches of mercury was
used for two periods of 5 minutes each, with one minute out of vacuum
between the applications. The treated mushrooms samples were blanched
for 5 minutes in boiling water after the treatment, cooled, drained
for 3 minutes on a slanted grid and weighed. The graph shows that
there is almost a direct straight line relationship between the
concentration of microcrystalline cellulose particles and the reduction
in the percentage of shrinkage with all of the other factors being
the same. The maximum concentration of 5% in these tests represents
the concentration with this particular material where the viscosity
approached a stiffness that made increasing the concentration impractical
from a processing point of view.
In FIG. 2, the results of a series of tests are graphically represented
in which the depth of the vacuum was varied between 20 inches of
mercury and approximately 29.5 inches of mercury. A 4%, by weight,
suspension of AVICEL CL-611, was used in all cases and the vacuum
was applied for two 5 minute periods with 1 minute period out of
vacuum between the vacuum applications. The figure graphically shows
that the reduction in shrinkage after blanching and cooling in this
case is substantially a function of the depth of the vacuum application
used and substantially correlates to the percentage of air that
was not drawn out by the vacuum with the results sharply improving
as a maximum vacuum level was achieved. Expressed as a ratio of
the amount of air remaining in the container, a vacuum of 29.5 inches
of mercury exhausts almost half of the air that still remains under
a vacuum of 29 inches of mercury.
In FIG. 3, the results of a series of tests are presented graphically
in which the duration of a single vacuum application was varied
from time periods of 5 seconds to 5 minutes. A water base suspension
of 4% by weight AVICEL CL-611 was used in all cases and the results
are shown after blanching and cooling of the mushroom samples. The
results are charted for a number of different vacuum levels which
are individually labeled. The results show that under moderate vacuum,
several minutes were required to widthdraw the maximum amount of
air from within the mushroom that that particular vacuum level was
capable of evacuating. Under deeper vacuum applications the air
within the mushrooms is withdrawn to its particular maximum evacuation
in a much more rapid time period. This is most likely due to the
greater difference in relative air pressure between the interior
and exterior of the mushrooms allowing the air to force its way
out more rapidly toward the minimum evacuated pressure.
Under all of the vacuum levels good results were obtained after
as short a duration as 5 seconds. Moderate vacuum levels required
up to 5 minutes to achieve substantially the same results as in
the tests shown in FIG. 2, wherein two 5 minute periods of vacuum
were used in all cases. Under greater vacuum, substantially the
same results were obtained in as little as 20 seconds as were achieved
in the tests reported in FIG. 2. Deeper vacuum levels can be expected
to achieve increased results over those shown in the graph, although
a vacuum lower than that which would cause the water, or other vehicle,
to freeze would be inadvisable. The vapor pressure of water at 0.degree.
C. is approximately 4.6 mm of mercury absolute, while the maximum
vacuum that was used in the tests corresponds to approximately 12
mm to 13 mm of mercury absolute. Use of deeper vacuum, while it
can be expected to achieve somewhat better and quicker results is
neither essential nor easily practicable in commerical sized production
All of the test results up to this point have dealt with mushrooms
that were close to 24 hours in storage after harvest. In FIG. 4,
the results of a series of tests are presented in which samples
of the same lot of mushrooms were withdrawn and tested along with
control samples at different time periods after harvest. The mushrooms
were held after harvest under good commercial cold storage facilities
specifically designed for mushrooms in which the temperature was
maintained at approximately 33.degree. F. and a high humidity level
was maintained. All of the treated samples were processed using
a 4% concentration of AVICEL CL-611 with two 5 minute vacuum applications
and a 1 minute period between vacuum applications for uniformity.
As can be seen in FIG. 4, the amount of shrinkage experienced during
processing can vary widely in the same lot of mushrooms dependent
upon the length of time they have been kept after harvest prior
to processing. The mushroom samples treated by the present process
and those processed in a normal commercial fashion show a steady
relationship of shrinkage between them regardless of the period
of storage. The entire sample lot of mushrooms used in this series
of tests lost weight due to continued respiration during the storage
period, and the quality as judged by showing of blemishes, open
veils, etc., deteriorated also. Adjustment was not made during the
rest period for changes of weight of the entire sample lot during
the storage period. This overall weight loss would have leveled
out the resulting curves somewhat, but would not have reflected
any change in the relationship between the shrinkage of the treated
and control samples.
Additional testing was performed on a number of additional materials
having all, or all but one of the particular physical properties
of microcrystalline cellulose as AVICEL CL-611 to illustrate the
particular combination of properties required for successful implementation
of the process.
There are a very limited number of materials that are commercially
available which are hydrophilic, non-water soluble, and have a reliably
measurable particle size in the micron and submicron range.
The silicas, as silicon dioxide, are available in a wide range
of uniform particle sizes from various manufactures. These fine
power-like particulates are generally used in food products as anti-caking
and flow improving agents in dry granular materials such as cake
mixes, breading, salt and sugar. They have a high affinity for water
and effectively pull moisture from the other materials such as flour
to make it free flowing. These silicas were obtained from a number
of manufactures in grades having uniform particle sizes ranging
from 15 microns down to 0.007 microns.
FIG. 5, graphically represents the results of a series of test
samples using different sizes of silica dioxide particulates. In
each case the silicas were suspended in water in concentrations
of 5% by weight concentrations. In cases where the particle sizes
were large enough that they tended to settle out of suspension up
to 0.4% of sodium carboxymethyl cellulose gum was added to the suspension
in duplicate tests to maintain the suspension. Since the test results
did not vary between those with and without the sodium carboxymethyl
cellulose gum they are recorded on the graph at the same point indicating
the silicadioxide concentration.
The tests all used two 5 minute periods of vacuum application of
approximately 29.5 inches of mercury with a 1 minute period between
the vacuum applications. The results are reported after blanching
and cooling of the mushroom samples.
As can be seen in FIG. 5, the silicadioxide in uniform particle
sizes of 2 microns diameter and larger had no effect in reducing
the shrinkage of the mushroom samples. In fact, the silicadioxide
which was in particle sizes too large to penetrate the mushrooms
actually appeared to have drawn water from the mushrooms as these
tests resulted in a greater shrinkage than the control batches which
were processed in a conventional manner.
The silicadioxide suspensions containing uniform particle sizes
less than 2 microns in diameter conversely had a dramatic effect
in reducing the shrinkage which was almost equal to that obtained
with the AVICEL CL-611.
A series of tests were also performed in which the concentration
of silicadioxide particulates were varied from 0.5% to over 10%.
The results of these tests for samples with particle sizes of 2
microns and larger were essentially the same as the results shown
in FIG. 5. The tests using silica dioxide particles under 2 microns
size showed a close relationship between the particle concentrations
and the shrink similar to that illustrated in FIG. 1. Greater concentrations
of these particles naturally resulted in increase in viscosity of
Microcrystalline cellulose is available from FMC corporation in
a number of types and grades other than type CL-611. FIG. 6, shows
the results of a series of tests using AVICEL type PH-105 microcrystalline
cellulose. AVICEL PH-105 has an average particle size of approximately
20 microns and contains no protective hydrocolloid such as sodium
carboxymethyl cellulose gum. Tests were run on this material at
various concentrations in water both with and without the addition
of 0.4% sodium carboxymethyl cellulose gum since the particles tend
to settle out of a simple water suspension at their initial size
range. Only a small reduction in the percentage of shrinkage was
noted over that of the control in any concentration.
The 20 micron average particle size of this material comprises
smaller particles bound together in large rod shaped or irregular
bundles or clumps. The chemical bonding between the individual particles
requires extremes of high shear application in order to reduce it
to the smaller individual particles without chemical processing.
A laboratory size colloid mill with a 2 inch diameter flat rotor
set approximately 0.5 mm from a parallel flat stator and operating
at approximately 18,000 RPM was used to break down this material.
A 5% suspension of AVICEL PH-105 was passed through this colloid
mill a number of times and periodic sample portions of the suspension
were withdrawn for microscopic inspection and testing on samples
As seen from the test results graphically represented in FIG. 6,
the AVICEL PG-105 suspension resulted in continually better shrinkage
reducing results as the material was comminuted in the colloid mill
to smaller and smaller particles which were broken up from the beginning
aggregate clumps and bundles. Microscope slides were made at each
stage of the milling and testing procedure and confirmed that an
increasingly large portion of the visable particles were extremely
small in size as the milling proceeded. After 40 passes through
the mill the microscopic examination of this material appeared nearly
identical to slides of AVICEL CL-611 under an optical microscope.
The test results also progressively approached those experienced
with AVICEL CL-611.
A number of additional materials were tested to confirm the activity
in reducing shrinkage of processed mushrooms of extremely small
non-water soluble particulates which are hydrophilic.
A pound of commercial dry spaghetti was placed in a Waring blender
and run at high speed for 30 minutes, resulting in a fine powder.
The powder was mixed with 6 cups of cold water in the blender and
run at a low speed for 1 minute. The resulting suspension was allowed
to settle for 10 minutes. The vast majority of the particles settled
out of the suspension leaving a cloudy supernatant water layer in
the container. Approximately 5 cups of the water, containing the
still suspended smallest particles, were poured off and divided
into two portions. One portion was used immediately to treat a sample
of mushrooms by the process using two 5 minute vacuum applications
of approximately 29.5 inches of mercury with a 1 minute period out
of the vacuum in between applications. The remaining settled-out
particles were at the same time mixed with a further 5 cups of cold
water in the blender, divided into two portions, and one portion
was used to treat another sample of mushrooms.
The mushrooms treated with the supernatent liquid suspension of
the smallest particles lost 11% of their weight after blanching
and cooling. The mushrooms treated with the suspension of the remaining
particles lost 22% of their weight after blanching and cooling.
The control sample lost 27% of their weight after blanching and
The remaining portions of the supernatent liquid and the suspension
of larger particles were tested again after having been stored under
refrigeration for 24 hours. At this time there was no significant
difference between either of these second test batches and the accompanying
control sample after blanching and cooling.
Microscopic examination of the suspension immediately after initial
mixing with water, revealed particles in sizes of approximately
4 microns and smaller, in irregular, sharp, mostly cubic shapes
almost exclusively in the decanted liquid. The liquid containing
the settled particles contained a small percentage of the smaller
size particles with the majority appearing to be larger than 20
microns. The concentration of the smaller particles in the supernatent
suspension was not determined accurately, but on the basis of comparison
of microscopic slides, with other known materials, it is believed
to be less than 1%.
Microscopic examination of the two portions after 24 hours refrigerated
storage, revealed that particles in both portions had swelled, lost
their sharp angular shapes, and were markedly larger in size.
Essentially identical tests using dry corn, dry rice and oriental
edible rice paper were made similar to that above using spaghetti.
The results of these tests parallelled closely the results of the
test results using the spaghetti.
A number of additional materials that have all but one of the particular
properties found to be successful in reducing shrinkage in mushrooms
were tested. These materials were unsuccessful in reducing shrinkage
by more than an insignificant 1% to 3% in any of the tests on a
repeatable basis. The following materials are representative of
these materials, most of which are either of particle sizes larger
than 2 microns, or are water soluable either in cold water or immediately
upon application of heat or are not hydrophilic. Starches were unsuccessfully
tested as common starches, modified starches and pregelatenized
starches from corn, wheat and potatoes. Xanthan gum, undenatured
protein such as Pro 80, Pay Gel 90 and Pro Fam were also treated
unsuccessfully as well as denatured whey powder of approximately
50 microns average size. Dry powdered Soy Lecithin as well as Soy
Lecithin in an oil base was also tested unsuccessfully.
Cigarette and cigar ashes were collected and also used in a series
of tests in substantially the same manner as those run on other
materials tested. This ash is extremely fine in nature, easily frangible,
hydrophilic, and readily disperses in water, while being non-soluable.
A 5% suspension of this ash was run in a blender at high speed
for 10 minutes. After stopping the blender, floating particles which
had been incompletely burned to ash were skimmed from the top. Microscopic
observations of the water suspended matter, showed a wide range
of particle sizes from approximately 100 microns down to apparent
sub-micron particles. The mixture was allowed to stand for 2 minutes
resulting in the larger particles settling out, and leaving the
remaining suspended minute particles in a concentration estimated
at less than 1%. This suspension was used on a test sample of mushrooms,
using a standardized procedure of two 5 minute vacuum applications
with a 1 minute period out of vacuum between the applications. After
blanching and cooling, a shrinkage of 13% was recorded as compared
to 27% for the control sample.
Microcrystalline chiten as described in U.S. Pat. No. 4,034,121
was prepared from crab shells. Tests run with this material exhibited
characteristic results similar to those reported for AVICEL PH-105
with the results improving as the average particle size was reduced
by passing the suspension through the small colloid mill a number
of times. Due to problems in preparation of this material and limitations
of the laboratory facilities available the inventors were unable
to accurately determine the purity and concentration of this material
as prepared. Microscopic examination of slides during the processing
revealed close similarity in particle size to that experienced during
similar tests with AVICEL PH-105.
It can be seen from the results of testing that a significant number
of materials have the capability of reducing shrinkage in mushrooms
during thermal processing. While vacuum has been shown to be a most
effective method of producing an infusion of these materials into
the mushrooms, pressure application followed by rapid, almost explosive
release of the pressure has also been shown to be effective in producing
an infusion of microscopic particulates into mushrooms. Tests were
performed using pressure and rapid pressure release on the silica
dioxide materials of less than 2 microns in size and the dry spaghetti
supernatent suspension. These test results paralled those reported
in Table 1, showing comparison of results using AVICEL CL-611 with
pressure and vacuum methods.
The materials that have been shown to be effective in producing
the shrinkage reduction have a number of particular properties in
common despite their composition being variously plant, animal and
mineral in nature. While some of these materials, such as cigarette
and cigar ashes and fairly high concentrations of silicadioxide
would not yield products particularly suitable for consumption as
food; the results of their testing is given to illustrate the particular
properties required for success in the process, and these particular
materials are not especially endorsed by the inventors, for human
food use, as described. These materials are all particulate in nature,
and to be effective the particles must be reduced in size until
the majority are less than approximately 2 microns in size and may
be at least as small as 0.007 microns in size while still retaining
their effectiveness in the process. The particles are not soluble
in the infusion vehicle, which was water in this series of tests,
and must remain undissolved under conditions of thermal processing
or cooking; although in the case of the spaghetti and like materials,
they may swell and soften during the cooking, without losing their
effectiveness. The particles must be readily dispersible in the
liquid vehicle and must have an affinity for water generally referred
to as being hydrophilic.
The exact mechanism within the mushroom that causes the reduction
in shrinkage when infused with the microscopic particulates is not
completely understood. It may be that the intermycellular spaces
are propped, much as oil wells are propped by injection of beads.
It may also be that the intermycellular pores are blocked, and size
loss and water loss during cooking is prevented in this manner.
A number of additional materials that have all but one of the properties
of the materials found to be effective in reducing shrinkage in
mushrooms were tested. These materials were unsuccessful in reducing
shrinkage by more than an insignificant 1% to 2% on a repeatable
basis, this shrink reduction being obtainable with water alone.
The following listing is representative of these materials, starches,
from corn, wheat and potatoes. These included common starches, modified
starches and pregeletinized types. Protein materials in extremely
fine but not submicron particles sizes in types that are not water
soluable such as PRO 80, Pay Gel 90, and Pro Fam. The particle sizes
of these materials range from 50 microns down to approximately 10
It is readily appreciated that the information presented by this
invention can be of considerable value to the mushroom processing
Mushrooms may now be processed by either a rapid vacuum, or a low
order pressure infusion, to reduce weight loss substantially.
Frozen mushrooms may be processed according to this invention to
reduce shrinkage and puddling upon subsequent cooking.
Both frozen and canned mushrooms may now be produced having a more
desirable and tender texture than previously available.
While this invention has been described by means of a plurality
of examples as to methods and materials, it is obvious that other
similar materials and methods may be employed to accomplish similar
results to those taught in this specification.